Method and apparatus for making fiber optic couplers

ABSTRACT

A method is disclosed for applying glue to a fiber optic coupler composed of a plurality of contiguously extending optical fibers, the fibers extending though the bore of a tube and through a longitudinally adjacent coupling region where the tube is collapsed around the fibers, the fibers being fused together in the coupling region, the diameters of the fibers in the coupling region being smaller than the diameters thereof in the bore. The method comprises: holding the coupler, and simultaneously injecting glue into both ends of the tube bore; wherein the coupler is oriented vertically, the glue being injected into the bore ends by positioning a hollow needle at each of the bore ends, the glue flowing through the needle in the bore at the top end of the tube at a rate greater than it flows through the needle in the bore at the bottom end of the tube.

This is a division of application Ser. No. 09/043,758, filed Mar. 25,1998, now U.S. Pat. No. 6,092,394, which was the National Stage ofApplication No. PCT/US96/15254, filed Sep. 16, 1996 and claims thebenefit of U.S. Provisional Application No. 60/004,647, filed Sep. 29,1995.

BACKGROUND OF THE INVENTION

The present invention relates to the automated manufacturing of fiberoptic couplers.

Overclad fiber optic couplers are a type of fused fiber coupler whereinthe coupling region is enclosed within a layer of matrix glass whichstrengthens and encloses the coupling region. To form an overclad fiberoptic coupler, the stripped portions of a plurality.of fibers areinserted into the bore of a glass capillary tube to form a couplerpreform. The tube bore has enlarged funnel-shaped end portions thatfacilitate the insertion of optical fibers. The midregion of the couplerpreform is heated to collapse the tube onto the fibers; the couplerpreform is then stretched until the desired coupling characteristics areobtained. Various types of overclad fiber optic couplers and methods ofmaking such couplers are disclosed in U.S. Pat. No. Re 35,138, U.S. Pat.Nos. 4,902,324, 4,979,972, 5,011,251, 5,251,276 and 5,268,014. Themethods disclosed in these patents include many manual operations.

In accordance with conventional practice, the manually operated fiberdraw apparatus has been oriented such that the tube is verticallypositioned. The fibers have been inserted into the tube either on-lineor off-line. The off-line fiber insertion process (U.S. Pat. No.4,902,324) requires that the fibers be tacked to the tube to prevent thefibers from moving with respect to the tube during the step oftransferring the coupler preform to the coupler draw apparatus. Thetacking glue can cause problems in the resultant coupler. Moreover, theoff-line method requires additional steps to transfer the tube to thedraw apparatus. The previously employed methods of inserting fibers intothe tube either on-line or off-line have been tedious, time consumingprocesses that are sensitive to the manipulations of each operator. Thiscan affect process reproducibility and thus the optical characteristicsof the couplers.

Optical fibers must be prepared prior to inserting them into the tube.The protective coating is removed from the portion of the fiber that isto be positioned within the tube during the coupler drawing operation.If the bare portion of the optical fiber is at the end of the fiber, itis preferred that it be provided with a low reflectance termination. Anoff-line process for forming such a termination is disclosed in U.S.Pat. Nos. 4,979,972 and 5,011,251. Also, the bare fiber portions must befree from contamination. Manual performance of these fiber preparationsteps is time consuming and is subject to the particular manipulationsof the operator.

During the stripping of coating from the fibers, the termination offibers, and the insertion of the stripped portions of fibers in theoverclad tube, the fibers must be precisely positioned.

In the manual technique for making overclad fiber optic couplers, thefibers were threaded through the glass tube, the tube was clamped intothe draw apparatus. Thereafter, the fiber pigtails extending from theglass tube were inserted through vacuum attachments which were thenaffixed to the ends of the tubes. Such vacuum attachments are unsuitablefor an automated apparatus for manufacturing fiber optic couplers. Apreferred heat source for forming overclad fiber optic couplers has beena ring burner that directs flames inwardly toward the glass tube.Heretofore, the glass tube has been manually inserted through the ringburner, and its ends were then clamped. Such a burner is not suitablefor use in a fully automated apparatus.

In an automated fiber optic coupler manufacturing process, couplers canbe made at a greater rate than they could be made by the aforementionedmanual process. The heat source must be activated during the stretchingof each coupler. This tends to cause the temperature of certain parts ofthe apparatus near the heat source to become hotter than they did in themanual process. Some of those apparatus parts and the coupler epoxy canbe damaged by the higher temperature or can be dimensionally alteredwhereby process reproducibility is affected. Precautions must be takento avoid such heat induced damage.

After the coupler has been formed by stretching the overclad tube andfibers, a glue such as an ultraviolet (UV) curable epoxy is insertedinto the uncollapsed ends of the tube bore to provide the fibers withpull strength. Conventional off-line epoxy applying and curingtechniques are not suitable for use in a fully automated coupler makingprocess since they do not result in the application of a sufficientamount of epoxy into both ends of the bore, and since they are timeconsuming processes.

SUMMARY OF THE INVENTION

In view of the above mentioned disadvantages of conventional methods ofmanufacturing fiber optic couplers, it is an object of the presentinvention to provide an apparatus and method of precisely andautomatically manufacturing a fiber optic coupler having predeterminedcoupling characteristics. Another object is to provide a couplermanufacturing apparatus and method in which opportunities for operatorcaused process inconsistencies are minimized or eliminated.

The present invention-relates to various apparatus components and methodsteps for making fiber optic couplers. Utilization of the invention inits entirety results in the completely automated production of a fiberoptic coupler. However, portions of the inventive method and apparatuscan be used to improve conventional methods of the type described above.Whereas the present invention is described in conjunction with themanufacture of overclad fiber optic couplers, certain of the apparatuscomponents can be employed in the manufacture of fused biconic taperedcouplers of the type wherein two or more fibers are fused together andelongated, without the use of an outer protective glass tube.

The present invention relates to an apparatus for the automatedmanufacture of fiber optic couplers. Fiber insertion means includingadjacently disposed fiber guide tubes insert optical fibers into a glasstube. The fiber guide tubes have fiber input and fiber output ends, theoutput ends being movable longitudinally with respect to the bore of theglass tube. Means is provided for delivering the optical fibers to theinput ends of the fiber guide tubes, with the first ends of the fiberspassing through the fiber guide tubes and being deliverable from andretractable into the second ends of the guide tubes. Means is providedfor sequentially tensioning each of the optical fibers and for strippingprotective coating from the tensioned length of each of the fibers. Theapparatus includes coupler draw means that is provided with upper andlower chucks for securing the glass tube at its end regions. The chucksare movable in opposite directions. First and second vacuum seal meansevacuate the bore and maintain closed the ends of the glass tube afterthe stripped regions of the fibers have been inserted into the bore.Heating means heats the glass tube. Programmable control means controlthe operation of the apparatus.

The coupler draw means can include an upper clamping bar that engages anupper V-groove provided in the upper chuck and a lower clamping bar thatengages a lower V-groove provided in the lower chuck; the clamping barsapply a repeatable level of force to the glass tube to secure it in thev-grooves.

The apparatus can include transfer means for transfering a glass tubefrom a storage magazine to the chucks. This apparatus can include aholding member provided with a groove, delivery means for delivering atube from the magazine to the groove, and clamping means for gripping atube. Means can be included for accurately locating the glass tube inthe groove. When it is in a first position, the clamping means engagesthe glass tube held in the groove. The clamping means then moves to asecond position and places the glass tube in the chucks of the couplerdraw means.

The means for delivering the optical fibers to the fiber insertion meanscan include at least two optical fiber supplies, and a fiber feedmechanism for paying out a predetermined length of each of the opticalfibers from the sources to the fiber insertion means. The programmablecontrol means controls the fiber delivering means, whereby it measuresthe optical fibers to the predetermined lengths. That is, preciseamounts of fiber are advanced from or retracted into the fiberdelivering means.

The fiber feed mechanism can include input guide tubes for receiving theoptical fibers from the reels, and output guide tubes that are connectedto the fiber guide tubes of the fiber insertion means. A fiber extendingbetween the input and output guide tubes is disposed between an idlerroller and a motor driven roller. When the idler roller engages themotor driven roller, the fiber is delivered to or retracted from theoutput guide tube. Fittings are connected to the output guide tubes forintroducing a gas therein for reducing friction between the fiber guidetubes and the optical fibers.

A lubricant dispensing tube can be disposed adjacent the fiber feedtubes and extend a distance beyond the ends of the feed tubes tolubricate the bore of the glass tube as the optical fibers are insertedtherethrough.

The means for sequentially tensioning each of the optical fibers caninclude an upper and a lower stripping clamp between which a length ofeach of the optical fibers is sequentially clamped and tensioned, andthe means for stripping the protective coating from the optical fiberscan include a stripping nozzle movable transversely and rotatably withrespect to the length of optical fiber that is tensioned between thestripping clamps. The stripping nozzle emits a jet of hot inert gas tostrip the protective coating away from the length of fiber as the nozzlemoves along the coated fiber.

The apparatus can include means for providing a low reflectancetermination on an optical fiber. A ball termination torch is verticallyand horizontally movable with respect to the optical fibers tensionedbetween the stripping clamps. After the torch severs the fiber, thestrippingclamps retracting in opposite directions.

Bottom clamp means can be provided for clamping one or more of theoptical fibers that extend from that end of the glass tube remote fromthe fiber insertion means.

The heating means is preferably located away from the chucks. After thestripped portions of the fibers are positioned in the tube bore, theheating means moves to a position adjacent the chucks. The heating meanscan be formed of two sections that close and surround the glass tube.

The upper and lower chucks partially shield the glass tube from theheating means, and in addition, the chucks are maintained at acontrolled temperature by water-cooling to enhance processreproducibility.

After the midregion of the glass tube has been heated, the chucks aremoved in opposite directions to stretch the tube. The means fordelivering fibers and the upper chucks are preferably mounted on a firstmovable stage, and the lower chucks and the bottom clamp are preferablymounted on a second movable stage, whereby the means for deliveringfibers and the bottom clamp move in opposite directions as the tube isstretched.

The apparatus can include dispensing means for dispensing glue into thebore of the glass tube, after a coupler has been formed and means forcuring the glue after the glue has been dispensed into the bore. Themeans for curing the glue can comprise a UV light source sequentiallypositioned at each of the ends of the glass tube.

A further embodiment includes first and second fiber insertion means,each capable of inserting at least two optical fibers into a glass tube.The first and second fiber insertion means are each-provided with atleast two adjacent fiber guide tubes that are movable longitudinallywith respect to the tube bore. Means are provided for moving the firstand second fiber insertion means laterally with respect to the bore.This apparatus is especially useful when used in conjunction with firstand second means for forming stripped regions in each of the opticalfibers. The first fiber insertion means can be disposed adjacent theglass tube when the second fiber insertion means is disposed adjacentthe second means for forming stripped regions.

Yet another embodiment pertains to an apparatus for modifying an opticalfiber. It includes means for delivering an optical fiber to a fiberguide tube such that the fiber can move out of and into the fiber guidetube. Means is provided for moving the fiber guide tube from one toanother of a plurality of work stations. This apparatus can includemeans for moving the fiber guide tube toward and away from the firstwork station.

The invention also pertains to a method of automatically manufacturing afiber optic coupler. A glass tube is placed into a coupler draw meanswhere its end regions are gripped by upper and lower chucks. At leasttwo optical fibers are delivered to a fiber insertion means. While alength of each of the optical fibers is tensioned between upper andlower stripping clamps, protective coating is stripped from each of theoptical fibers, and the fibers are then inserted through the glass tubesuch that the stripped regions extend within the bore. The ends of theglass tube are evacuated, and the tube is heated. The end regions of theglass tube are drawn in opposite directions to form a tapered couplingregion. The steps of the method are controlled by programmable controlmeans.

The glass tube can be gripped in the coupler draw means by securing oneof the tube end regions between an upper chuck V-groove and upperclamping bar, and securing the other end region between a lower chuckV-groove and a lower clamping bar, the upper and lower clamping barsapplying a force to the glass tube to secure the glass tube in the upperand lower V-grooves. The upper and lower chucks can be maintained at acontrolled temperature to improve process reproducibility.

The glass tube can be placed into the coupler draw means byautomatically transferring the glass tube from a glass tube storagemagazine to the draw means.

The optical fibers can be delivered to the fiber insertion means bypaying out each of the optical fibers from fiber sources to fiber guidetubes of the fiber insertion means. The fiber guide tubes can movelongitudinally with respect to the bore of the glass tube. A gas can beintroduced into the fiber guide tubes to reduce friction between thefibers and the tubes and to remove debris from the fibers entering theguide tubes.

A stripped region can be formed on a fiber by positioning the fiberguide tubes above a lower stripping clamp, and delivering a length of anoptical fiber is delivered through one of the fiber guide tubes to thelower stripping clamp which grips the fiber at a first location. Theguide tubes are moved upwardly so that the upper stripping clamp cangrip the fiber at a second location. The fiber is then tensioned betweenthe first and second locations. A jet of hot inert gas is directed ontoa predetermined region of the tensioned fiber to heat it and stripcoating therefrom.

A low reflectance termination can be provided on an optical fiber priorto inserting it through the glass tube. The fiber is tensioned betweentwo spaced points. A ball termination torch is moved from a givenlocation in a given direction with respect to the optical fiber suchthat a portion of the flame severs the fiber into two pieces each havinga tapered end. At least one of the tapered ends is retracted away fromthe other of the tapered ends. The torch continues to move such that theflame heats the retracted tapered end to cause it to becomeshortened-and rounded.

A lubricant is preferably dispensed into the glass tube when the opticalfibers are inserted therethrough. This can be done by disposing adispensing tube adjacent the fiber guide tubes, and dispensing thelubricant therefrom.

The method can further include dispensing glue into the uncollapsed endsof the bore of the glass tube after the tapered coupling region has beenformed. The glue can initially be cured by directing UV light beams ateach of the end regions of the glass tube while the glue is beingapplied to the ends of the bore, the flow of the glue stopping when itcontacts the light beams. The glue can be further cured by sequentiallypositioning a UV light source at each of the end regions of the glasstube after the glue has been dispensed into the bore.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1 and 2 schematically illustrate an automated fiber optic couplermanufacturing apparatus.

FIG. 3 illustrates the spacial relationship between FIGS. 4 through 7.

FIGS. 4 and 5 are front views of the top and bottom portion of theautomated fiber optic coupler manufacturing apparatus.

FIGS. 6 and 7 are enlarged views of the upper right portion and thecentral portion of the automated fiber optic coupler manufacturingapparatus.

FIG. 8 illustrates a capillary tube transfer aparatus.

FIG. 9 is a cross-sectional view of the capillary tube magazine.

FIG. 10 schematically illustrates the tube positioning apparatus.

FIGS. 11a and 11 b are side and top views, respectively, of thecapillary tube retaining chucks.

FIG. 12 is a schematic oblique view of the capillary tube retainingchucks and the vacuum seals.

FIG. 13 is an end view of the retaining tube.

FIG. 14 is a cross-sectional view taken along lines 14—14 of FIG. 13.

FIG. 15a is an end view in partial cross-sectional view of a fiber feedapparatus.

FIG. 15b is a cross-sectional view taken along lines 15 b—15 b of FIG.15a.

FIG. 16 is a cross-sectional view of an idler roller used in FIGS. 15aand 15 b.

FIG. 17 is a side view of a pair of fiber tensioning clamps used in thefiber stripping, severing and end terminating operations.

FIGS. 18a and 18 b are top views of the fiber tensioning clamps.

FIG. 19 illustrates the stripping nozzle positioning apparatus.

FIG. 20 schematically illustrates the operation of the coating strippingnozzle.

FIG. 21 is an oblique view of the apparatus that positions the fiber endtermination torch.

FIGS. 22, 23, 24 and 25 schematically illustrate the operation of thefiber end termination torch.

FIG. 26 is a front view of the vacuum seals.

FIG. 27 is a top view of the vacuum seals.

FIG. 28 is a cross-sectional view taken along lines 28—28 of FIG. 26showing the left upper vacuum seal.

FIG. 29 is a side view showing the relationship between the tuberetaining chuck and the upper right vacuum seal.

FIGS. 30 and 31 show side and top views, respectively, of the couplerdraw apparatus burner.

FIG. 32 shows a view taken along lines 32—32 of FIG. 31.

FIGS. 33 and 34 are.side and front views, respectively, of the epoxyapplication apparatus.

FIG. 35 is an oblique view showing the UV light source positioningapparatus.

FIG. 36 is a cross-sectional view of tube 12′ as it appears in thecoupler draw apparatus.

FIG. 37 is a partial cross-sectional view of a coupler duringapplication of epoxy to its ends.

FIGS. 38 and 39 illustrate guide tube arrangements for supplyingsix-around-one and eight-around-one fiber configurations.

FIG. 40 schematically shows a coupler manufacturing apparatus employingtwo stripping and terminating stations.

FIG. 41 schematically shows an apparatus for positioning an opticalfiber at a plurality of work stations.

DETAILED DESCRIPTION

Overview of Invention

A brief overview of the method and apparatus of the invention will begiven by referring to FIGS. 1 and 2 which schematically illustrate anautomated fiber optic coupler manufacturing apparatus 10. In connectionwith this description, as well as the following more detaileddescription, steps are described for making a 1×2 overclad fiber opticcoupler. All references to x, y and z directions refer to the axes thatare illustrated in various figures including FIG. 2.

(1) Tube transfer apparatus 11 including a tube gripper 14 delivers aglass capillary tube 12 from a storage magazine 13 to coupler drawapparatus 63 where its end regions are secured by upper and lower chucks64 and 65, respectively. The chucked tube is designated 12′.

(2) Fibers 16 and 17 are delivered from reels 18 and 19, respectively,by fiber feed apparatus 23 to fiber insertion fixture 50.

(3) The fibers are sequentially fed from the fiber insertion fixture toa strip/terminate apparatus 56 where the fibers are sequentially securedwithin clamps 57 and 58 so that a section of coated fiber is tensionedbetween the two clamps.

(4) Stripping nozzle 59 emits a jet of hot inert gas that traverses aregion of coated fiber to strip coating therefrom.

(5) When appropriate, end termination torch 60 severs the bare fiberthat extends between clamps 57 and 58 and forms a low reflectancetermination on one or both of the bare severed fiber ends.

(6) The fibers are inserted into the tube 12′ so that the bare portionsof the fibers extend within the bore of the tube. Valve 43 is actuatedto dispense drops of alcohol from source 42 through dispensing tube 44to the upper end of tube 12′ to lubricate the bore as the fibers passtherethrough. Bottom clamps 69 are employed to pull and hold taut one ormore of the fibers extending from the bottom end of tube 12′ while theyare being fed to the upper end thereof.

(7) The end of one or more fibers that extend through tube 12′ areaffixed to one or more optical fibers 47 which are connected to one ormore light sources in measurement system 46.

(8) Bottom vacuum seals 67 are closed onto the bottom end of tube 12′ towithdraw alcohol from the bore.

(9) Top vacuum seals 66 are closed on the top end of tube 12′ and thebore of tube 12′ is evacuated.

(10) Split burner 68 is ignited and closes around tube 12′ to heat itsmid-region.

(11) Top and bottom chucks 64 and 65, respectively, are traversed inopposite directions to stretch tube 12′ and form a tapered couplingregion.

(12) Vacuum seals 66 and 67 are opened.

(13) Light beams from upper and lower epoxy locating UV light sources(FIGS. 12 and 37) are directed toward the upper and lower ends ofstretched tube 12′.

(14) Epoxy dispensing apparatus 72 moves to draw apparatus 63, and epoxydispensers 73 and 74 are positioned at the top and bottom funnels oftube 12′. Epoxy is dispensed through needles into the funnels. As epoxyflows into the uncollapsed ends of the tube bore, the epoxy locating UVbeams cure and prevent penetration of epoxy into the bore beyond apredetermined depth.

(15) The epoxy dispensing apparatus is withdrawn, and UV light apparatus70 is sequentially positioned adjacent the top and bottom ends of thenewly formed coupler to cure the epoxy. The epoxy locating Uw beamsremain energized.

(16) The coupler body is released from the draw chucks. The fiberpigtails at the top of the coupler are metered to the desired length andare severed, whereby the coupler can be removed from the automatedmanufacturing apparatus.

Various components of apparatus 10 such as the motors, gas operatedcylinders, clamping devices and mass flow controllers for methane andoxygen are controlled by programmable controller 79.

Description of Components

All of the components of manufacturing apparatus 10 are secured eitherdirectly or by way of supports, brackets and the like to backplate 200.Not all supports are shown. The orientation of elements with respect tobackplate 200 is sometimes given relative to an x-axis, a y-axis or az-axis. Backplate 200 lies in the x-y plane. Movement of an element inthe +z direction means movement away from backplate 200 (out of thesheet of FIGS. 4 and 5).

FIGS. 8-10 show the tube transfer apparatus 11 in greater detail. Aslotted cylinder 84 is rotated ¹⁸⁰E and then back again by a doublepiston rotary cylinder (not shown). This type of cylinder consists oftwo pistons that provide linear motion that is converted to rotarymotion through a rack and pinion gear device. Capillary tubes 12 arestored in a magazine 13 and are gravity fed to a transfer position (thebottom of the stack of stored tubes) where they fall into slot 83.Magazine 13 sits in dispensing mechanism 82 which houses cylinder 84.When cylinder 84 rotates, a single tube is transferred to pick-upposition 85 in spaced V-groove members 86. A cylinder 87 is actuated tocause piston 88 to position one end of tube 12 against stop 89 toprecisely locate the tube. The location of stop 89 can be adjusted toaccomodate different tube lengths.

Mechanism 82 is mounted on stage 101 that can be vertically reciprocatedon slide 102 by actuating cylinder 103. Clamping device 93 is mounted ona stage 94 that can be reciprocated back and forth on slide 95 byactuating cylinder 96. Clamps 92 are biased open by a spring and areclosed by actuating a double piston (pancake) cylinder located withinmechanism 93.

Cylinder 96 is actuated to position clamps 92 around the tube that islocated in the pickup position in groove members 86. Mechanism 93 isactuated to cause clamps 92 to engage tube 12, and cylinder 103 is thenactuated to cause the Vgroove member 86 to be translated downwardly.Cylinder 96 is then actuated to retract the clamps away from themagazine.

Clamp slide 95 is mounted on an arm 107 that is rotatably connected tosupport bracket 108 by double piston rotary cylinder mechanism 106. Whenmechanism 106 is actuated, arm 107 rotates about 90 _(E) and positionsclamp mechanism 93 in alignment with the coupler draw apparatus 63 wherethe tube in clamps 92 is directly in front of the V-grooves of chucks 64and 65.

Various modifications could be made to the disclosed dispensingmechanism. The tubes would not need to be gravity fed if means such as aspring were employed to supply them to cylinder 84. Moreover, cylinder84 could be replaced by a wheel having a plurality of slots. A glasstube from the supply-of tubes would enter a slot of the slotted wheeland be rotated until it reached an orientation at which the tube wouldfall from the slot into grooves 86. Cylinder 84 could also be replacedby a pair of sequentially operated gates that are capable of preventingmovent of the first two tubes in the linear supply of tubes. A firstgate holding the last tube would retract so that the last tube couldroll to grooved member, while the next to last tube is held by a secondgate to prevent the remaining tubes from also rolling to the groovedmember. The first gate then moves into position while the second gateretracts to permit the supply of tubes to roll to the first gate.

Chucks 64 and 65 are shown in FIGS. 11a, 11 b, 12 and 29. None of thesupport members are shown in the schematic view of FIG. 12. The chucksinclude a mounting plate 110 and a V-groove plate 111. Through a seriesof support members (also see FIGS. 27 and 28) the mounting plates 110 ofupper and lower draw chucks 64 and 65, respectively, are affixed tovertically movable upper and lower draw stages 299 and 300, respectively(see FIGS. 4 and 5). All of the elements within the upper brackets ofFIG. 12 are connected to upper movable stage 299 by support member 283,and all of the elements within the lower brackets are connected to lowermovable stage 300 by support member 284. Tube clamping bar 113 ispivotally mounted in a recessed region adjacent plate 111 by a bolt 114that threads into bore 112. Rod 116 of cylinder 117 is pivotallyattached to bar 113.

After cylinder 96 (FIG. 8) has been actuated to position the tube (nowdesignated 12′) in the Vgrooves of the chucks 64 and 65, cylinders 117are actuated to cause bars 113 secure the tube in the grooves.

Since the tube had been-precisely positioned in groove member 86 of thetube transfer apparatus, the ends of the tube are vertically positionedto within about 0.1 mm of the desired location in the coupler drawapparatus so that operations such as epoxy application can be properlyperformed. Properly positioning the tube also ensures that the coatingedge of the stripped fiber will be positioned the proper depth in thetube funnel so that epoxy can be properly introduced into the funnel andbore of the tube.

The chucks are designed to achieve the automated loading of thecapillary tube while also enabling a repeatable load level to be appliedby bar 113 to the tube since bar 113 is actuated by air cylinder 117.The force applied by bar 113 to the tube can be controlled by regulatingthe air pressure applied to that cylinder.

The chucks partially shield the vacuum seals from the high temperatureflame. When the vacuum seals are closed, the elastomeric seals 288 areshielded from the flame by the chucks. The water cooling of the chucksallows the coupler draw process to have a relatively short cycle timesince the chucks would otherwise become so hot after a few couplers hadbeen made that process consistency could not be maintained. The coolantwater, which is pumped from a temperature controlled reservoir,maintains correct temperature regardless of timing differences betweenruns. Deviation of chuck temperature from a given temperature rangeaffects the optical properties of the resultant coupler.

Apparatus for delivering fibers is shown in FIGS. 1, 2, 15 a, 15 b and16. Fiber reels 18 and 19 are non-rotatably mounted and are sopositioned with respect to feed apparatus 23 that fibers 16 and 17,respectively, that are coiled thereon, pay out to the fiber feedapparatus. The ends of fibers 16 and 17 opposite those ends that aredelivered to fiber insertion fixture 50 constitute measurement pigtails20 and 21, respectively, which are connected to detectors in measurementsystem 46. This arrangement is made possible since the reels arerestrained from rotating. Management of the fibers extending betweenreels 18 and 19 can be facilitated by positioning guide funnels 15between the reels and the fiber feed apparatus. The large ends of thefunnels are positioned adjacent the spools. Optionally located in thesmall ends of the funnels are sponges 22 that are slitted or folded overto encompass the fiber that passes therethrough. The sponges, which arewetted with alcohol, wipe dust and debris from the fibers. Neither thefunnels nor the sponges are needed for proper operation of theapparatus. A commercially available air deionizer 33 removes staticelectricity from the fibers. Such air deionizers can be positioned atvarious locations on the apparatus to blow deionized air onto thefibers.

If rotatable fiber reels were employed, measurement pigtails 20 and 21could be connected to measurement system 46 by rotatable connectors.Moreover, the fibers need not be stored on reels. Rather, they could bemerely coiled or be stored in boxes.

The cross-hatched portions of FIGS. 15a, 15 b (except for the rollerassemblies) are aluminum plates that are fixedly located in theapparatus. Roller 24 is rotated by reversible stepping motor 25. Locatedadjacent roller 24 are idler rollers 26, 27 and 122 which are actuatedby gas operated cyclinders 28, 29 and 121. Roller 24 is provided with arubber sleeve 119, and the idler rollers are provided with rubbersleeves 120. Cylinders 28, 29 and 121 normally receive a compressed gasinput that biases rollers 26, 27 and 122 such that they are spaced fromroller 24. Means such as a spring could also be employed to perform thisbiasing function. Whereas only the two idler rollers 26 and 27 shown inFIG. 2 are needed to form a 1×2 coupler, the device of FIG. 15b alsoincludes two additional idler rollers 122 and their actuating cylinders121. To supply more than four optical fibers, apparatus 23 could beprovided with additional idler rollers. Alternatively, in addition toapparatus 23, another fiber feed apparatus similar to apparatus 23 couldbe employed in manufacturing apparatus 10. To feed ten fibers, forexample, apparatus 10 could employ two fiber feed apparatuses, eachfeeding five fibers.

Cylinders 28, 29 and 121 are affixed to roller mounting plates 123 thatare attached to movable stages 125 of ball slides. The fixed stages 124of those ball slides are attached to aluminum plates within the housing.The piston rods are threaded in nuts that are located within fixedyokes. Cylinder 31 is a pancake cylinder from which extend two posts 127that thread into the metallic block of the clamp 30 which is providedwith a synthetic rubber layer 128. Bar 32 is also provided with asynthetic rubber layer 129.

The ball slides described herein, which were made by Daedal, Inc.,Harrison City, Pa., include a stage having a U-shape cross-section and aball slide positioned within the stage. Ball bearings, which aresitutated in spaced openings in (racks) that separate the stage andslide, traverse along (tracks) in both the stage and the ball slide.

To feed optical fiber into fiber feed apparatus 23, the idler rollersand clamps 30 are retracted. The fiber is fed through an input guidetube 132, over the respective idler roller and into output guide tube133 which is connected to T-fitting 39. Output guide tubes 133 aresupported by brackets 131 that are positioned by spacers 130. Asufficient length of fiber is fed into the guide tubes to enable it toextend from the ends of the guide tubes at insertion apparatus 50.Clamps 30 are then closed. The protruding fibers can be cut by amechanism (not shown) in apparatus 10, or they can be manually severedby bending them sharply at the point where they extend from theirrespective guide tube. The ends of the guide tubes are sufficientlysharp that the fibers become severed at the ends of those tubes. This isthe starting position for the coupler making process.

T-fittings 38 and 39, located near the input ends 40 and 41 of the guidetubes, introduce a gas such as nitrogen, air or the like into thosetubes. Gas flowing from the input ends 40 and 41 blows dust and debrisfrom the fibers before they enter the tubes. Gas flowing through theguide tubes to the ends thereof at fiber insertion fixture 50 lowers thefriction between the guide tubes and the fibers.

Motor 25 could be a d.c. servo motor or any other motor that canaccurately rotate roller 24 and thus accurately position the fibers.Moreover, clamps 30 could be eliminated if a separate motor wereemployed for each set of rollers.

Fiber insertion apparatus 50 (FIGS. 2 and 4) is affixed to one end of asupport arm 55, the other end of which is connected to a stage 52 whichis vertically movable along track 54 as indicated by the arrow.Apparatus 50 includes a retaining tube 51 in which are disposed fiberguide tubes 35 and 36 and alcohol dispensing tube 44. Tubes 35, 36 and44 are secured to the end of tube 51 by epoxy 45 (FIG. 13). Tube 51 wasformed of 0.343 cm inside diameter, 0.419 cm outside diameter, 8 gauge304 stainless steel tubing. For delivering optical fibers having 250 μmoutside diameter coating, tubes 35 and 36 were formed of 0.043 cm insidediameter, 0.064 cm outside diameter, 23 gauge 304 stainless steeltubing.

Retaining tube 51 and fitting 49 are employed so that tubes 35, 36 and44 can easily be positioned relative to one another. However, retainingtube 51 and fitting 49 can be eliminated by merely gluing tubes 35, 36and 44 together into a triangular array as shown in FIG. 13. Theassembly of tubes can in turn be affixed to support arm 55.

As shown in FIGS. 13 and 14, the end of retaining tube 51 fits over thesmaller diameter portion of a brass fitting 49 and butts against theshoulder of the larger diameter end portion. Fitting 49 has a precisionbore the diameter of which is just large enough to receive tubes 35, 36and 44. Guide tubes 35 and 36 protrude a short distance from fitting 49.A drop 140 of alcohol is shown extending from dispensing tube 44 whichprotrudes farther than guide tubes 35 and 36 to prevent dispensedalcohol from flowing into the guide tubes.

Strip/terminate apparatus 56 is shown in greater detail in FIGS. 17, 18a and 18 b. The apparatus includes two air operated cam-action grippers151 and 152 which consisted of Sommer ultramatic cam-action grippersModel No. GP-19. Each gripper consists of an actuator mechanism 153 thatcauses appropriate movement of laterally movable members 154 alongcylinders 155. Affixed to members 154 are L-shaped members 156 to whicha fiber gripping elastomeric layer 157 has been applied.

Base plate 160 is mounted on stage 161 which is movable along slide 162which is secured to vertical support plate 163. Gas operated cylinder181 is mounted on stage 161. Piston 182 of cylinder 181 is threaded intoplate 163.

Mounted on base plate 160 are linear slides 165 and 166 on whichmounting brackets 167 and 168 are movably mounted. The extent ofmovement of the mounting brackets 167 and 168 is restricted byadjustable screw stops 169. Four Clippard gas operated pistons (modelNo. SM-3) 171-174 are mounted to brackets on base plate 160. Pistons 175and 176 are adapted to engage tab 179 protruding from stage 167, andpistons 177 and 178 engage tab 180 protruding from stage 168.

Stage 161 is normally retracted against support plate 163. cylinder 181is actuated to move stage 161 away from plate 163 to a position alongthe z-axis where fiber 17 (extending from guide tube 36) extends betweenclamps 156 (clamps 57 and 58 of FIG. 2). Mechanisms 154 are actuated tocause clamps 57 and 58 to close on the fiber. Gas operated pistons 172and 173 are actuated whereby pistons 176 and 177 engage tabs 179 and180, respectively. This applies forces to the tabs that tend to movestages 167 and 168 in opposite directions, whereby coated fiber 17 istensioned between clamps 57 and 58.

The apparatus for positioning stripping nozzle 59 is shown in FIG. 19.Stripping nozzle 59 is rotatably connected to support bracket 190 bydouble piston rotary cylinder mechanism 191. Support member 190 isaffixed to the rotatable stage 193 of rotating mechanism 194 that iscontrolled by motor 195. Mechanism 194 is supported by an arm 196 thatis affixed to stage 197 that is movable vertically along track 198 whenmotor 199 is energized.

When mechanism 191 is actuated by pistons 192, stripping nozzle 59rotates to the horizontal position. Actuation of rotary mechanism 194and motor 199 lowers stripping nozzle 59 and rotates it to a positiondirectly in front of coated fiber 17.

FIG. 20 illustrates the operation of stripping nozzle 59. The coatedoptical fiber 210 that was employed in the coupler manufacturing processwas a conventional silica-based single-mode optical fiber having-anoutside diameter of 125 μm. The optical fiber was provided with aurethane acyrilate coating 212 having an outside diameter of 250 μm. Asource 216 of inert gas such as nitrogen was supplied through filter 217and flowmeter 218 to the inlet pipe 223. A Convectronics Model 001-10002tube heater was employed. The diameter of the outlet end of the nozzlewas 1.76 mm. Nitrogen continually flowed at a rate of 20.9 standardliters per minute (slpm) into inlet pipe 223. Hot gas was dischargedinto vent 234 (FIG. 4) when the stripping nozzle was not in use. Thevoltage supplied to heater tube 220 was sufficient to provide a gastemperature that is adequate for melting the coating material. Atemperature of about 820_(E)C. is suitable for stripping a urethaneacyrilate coating. Stripping nozzle 59 was mounted on a supportapparatus 191 that provided it with the various degrees of motiondescribed in connection with FIG. 19. To simplify this description ofFIG. 20, apparatus 191 is described as being capable of rotating aboutaxis 222 as indicated by arrows 226 and 227 and being capable of movingalong axis 222 as indicated by arrows 228 and 229.

Coating material 212 was to be removed from coated fiber 210 betweenpoints a and b along a section thereof that was held between clamps 57and 58. Stripping nozzle 59 was rotated from its resting position to ahorizontal orientation. It then traversed downwardly and rotated towardthe coated fiber. Referring to FIG. 20, stripping nozzle 59 was rotatedabout axis 222 in the direction of arrow 226 until the jet of hot gasemanating from the tube heater nozzle 225 was directed a few millimetersto the side of coated fiber 210. After a short pause, it rotated toposition the jet at point a of the coated fiber and immediately began totraverse along axis 222 in the direction of arrow 229. The distancebetween the end of nozzle 225 and the coated fiber during the fiberstripping operation was about 2.86 mm. As the hot nitrogen jet emanatingfrom nozzle 225 moved along the coated fiber, coating material wassoftened and blown from the fiber. The removed coating material wasdischarged into vent 235 (FIG. 4). After coating material had beenremoved between points a and b along coated fiber 210, stripping nozzle59 rotated about axis 222 in the direction of arrow 227 so that hot gaswas no longer directed at the fiber. The exposed optical fiber 211 wassufficiently clean that it could be used in the coupler manufacturingprocesses without further treatment.

The low reflectance end termination apparatus of FIG. 21 forms on theends of optical fibers the low back reflection termination that isrequired for high performance optical components. Torch 60 is connectedto a vertical stage 241 by a support 240. Stage 241 is verticallymoveable along track 242 as motor 243 turns threaded shaft 244. Verticaltrack 242 is affixed to stage 245 that is horizontally moveable alongtrack 246 when motor 247 rotates threaded shaft 248. Track 246 isaffixed to the vertical back plate 200 by bracket 249. In its inactivestate, end termination torch 60 is positioned as shown in FIG. 4.

The operation of the fiber severing and end termination torch 60 isillustrated in FIGS. 22-25. Torch 60 had a size 2 tip (0.17 mm nozzleopening). A methane flow rate of 19 standard cubic centimeters perminute (sccm) and an oxygen flow rate of 25.5 sccm to the torch producedan adequate flame. The port velocity of the torch cannot be too high, orthe tapered portion of the severed fiber will form a hook. Coated fiber210 that had been.stripped as described in conjunction with FIG. 20 istensioned between clamps 57 and 58. As previously described inconjunction with FIG. 17, cylinders 172 and 173 had been actuated (whilecylinders 171 and 174 remain non-activated), whereby pistons 176 and 177bear against tabs 179 and 180, respectively, tending to cause clamps 57and 58 to move in opposite directions and thereby tension the fiber.After stage 241 had lowered torch 60 to the correct vertical position,stage 245 moved at a rate of 38.1 cm/minute to cause flame 260 to passover fiber 211 at a rate sufficiently fast that the flame hadessentially no effect on the fiber. The −z movement of the torch wasstopped when the visible, peripheral portion of flame 260 was about 0.25cm behind the fiber as shown in FIG. 23. Motor 247 was reversed, andstage 245 moved in the +z direction at a rate of 3.81 cm/minute. As thetorch moved forward in the direction of arrow 263, the outer portion ofthe flame moved to a position shown in FIG. 24, thereby severing andforming tapered end regions 265 and 266. When the fiber became severed,clamps 57 and 58 moved in the direction of arrows 271 and 272 until theclamping mechanisms were stopped by set screws 169. When flame 260reached the position illustrated in FIG. 25, tapered regions 265 and 266had been heated to an extent sufficient to cause rounded endterminations 267 and 268 to form under the influence of surface tension.The resultant low reflectance termination had a typical back reflectionless than about −55 dB.

If clamps 57 and 58 move the same distance (about 1-2 mm has been foundto be suitable), a low reflectance ball termination will form on both ofthe tapered regions. If only top tapered region 265, for esample, is tobe provided with a ball termination, clamp 58 can be moved a greaterdistance (perhaps a few centimeters) while clamp 57 moves about 1-2 mm,whereby only tapered region 265 is provided with a low reflectancetermination, and tapered region 266 is moved out of the influence of theflame.

FIGS. 26-29 as well as FIG. 12 illustrate the operation of the apparatuswhich closes vacuum seals 66 and 67. Only the upper vacuum seals areillustrated in FIGS. 26-29. FIG. 12 is a schematic diagram that does notinclude any mounting brackets; it merely illustrates the relativepositions of the chucks, vacuum seals and an initially operating pair ofuv light sources. Elements included within the top bracket (see leftside of drawing) are affixed to the top draw stage 299. Elementsincluded within the bottom bracket are affixed to the bottom draw stage300. Seal 66 is mounted by a bracket 286 to a stage 280 that is capableof horizontal movement along slide 285. Slide 285 cannot be seen inFIGS. 26 and 27 since it is located within stage 280 when the apparatusis in the neutral position that is illustrated. Ball slides 285 areaffixed to support plate 283 by way of seal movement mounting plate 282.Support plate 283 is affixed to upper stage 299 of the coupler drawapparatus. To facilitate the precise positioning of the upper and lowerdraw stages 299 and 300 with respect to eachother, they can be affixedto a mounting plate (not shown) which is, in turn, mounted to backplate200.

The upper left vacuum seal 66 is shown in FIGS. 26 and 28. Anelastomeric seal 288 extends around the periphery of a face of metalbackplate 289. Elastomeric seal 288 forms, along with the face of backplate 289, a cavity 296. A bore 290 in backplate 289, which communicateswith cavity 296, is connected to blead valve 76 (FIG. 2). Blead valves76 and 77 allow a controlled flow of air to enter upper left vacuum seal66 and lower left vacuum seal 67, respectively. Elastomeric seal 288 isformed of Dow 591LSR, a flame resistant liquid silicone rubber. Seal 288is glued the surface of backplate 289 with the same liquid siliconerubber from which the seal is made. The seal has four holes into whichfour locating pins 292 project in order to correctly position the sealon the face of backplate 289. A cylindrical. depression 287 at thebottom of the elastomeric seal receives the top of the capillary tube12′.

The upper right vacuum seal 66 (FIG. 29) is identical to the left uppervacuum seal except that bore 291 in backplate 289 is connected to avacuum source. FIG. 29 also shows the relationship between the vacuumseal and the draw chuck 64. Chuck mounting plate 110 is affixed tosupport plate 283.

Associated with each vacuum seal is an air cylinder 293, the piston rod294 of which is affixed to a bracket 295 extending from bracket 286.Cylinders 293 can be actuated to open or close the vacuum seals.

FIG. 12 shows two UV light sources 297 that are traversed to theposition shown after the coupler has been drawn and the chucks have beenopened. Sources 297 are turned on before epoxy is inserted into the endsof the tube bore, and they are turned off, along with sources 370 and371, after the epoxy has been cured. The upper and lower UV sources 297are attached to upper and lower stages 299 and 300, respectively, byfour-bar links, whereby those UV sources both retract in the directionof arrows 297 a and move away from eachother after the epoxy has beencured. The function of sources 297 is further described in U.S. Pat. No.5,268,014, which is incorporated herein by reference.

Burner 68 is shown in FIGS. 30-32. The burner comprises two sections 310and 311 which are affixed to the laterally moving members 312 and 313 ofPHD cam action gripper mechanism 315. The burner, shown in its openposition, can be closed by actuating burner close mechanism 314.Sections 310 and 311 include annular regions 316 and 317, respectively,each having a plurality of flame ports 319. The distribution channelswithin the burner halves were symmetrical, whereby the flames emanatingfrom each of the ports were substantially identical. Gas and oxygen aresupplied to each burner section through lines 320.

Burner close mechanism 314 is affixed to a bracket 321 which is affixedto stage 322. Stage 322 moves in the direction of the double headedarrow along slide 323 which is affixed to support 324. Support 324includes a rib 325 having an opening in which cylinder 327 is fixedlymounted. The end of cylinder rod 328 is connected to a yoke at the endof bracket 321. Support 324 is secured to back plate 200.

It is convenient to ignite the flame when the burner is in its retractedposition shown in FIG. 30. During ignition (and during movement of theburner to tube 12′) methane flows at the level that would be required toheat tube 12′, but oxygen flows at a reduced level to reduce the amountof heat produced. When the gas and oxygen are turned on, these gasesflow up the lower portion of flame shield 330 to silicon carbideresistance ignitor 329. When the gases ignite, the flame propagates inthe +z direction through the channel formed by the flame shield toprotect those components located above the burner. After the burnerhalves close around tube 12′, the oxygen flow is increased to provide asufficiently hot flame to soften the tube so that it can collapse and bestretched.

Epoxy application apparatus 72 is shown in FIGS. 33 and 34. Epoxyapplication devices 340 and 341 are TS 5000 rotary microvalves, whichare electrically motorized auger feed mechanisms. Epoxy is delivered tomechanisms 340 and 341 from sources 360 and 361, respectively, which arepressurized by air supplied by valves 362 and 363, respectively. Epoxyfrom mechanisms 340 and 341 deliver the epoxy to the ends of the couplerthrough hypodermic needles 338 and 339, respectively (not shown in FIG.34). Devices 340 and 341 are mounted by angular and horizontaladjustment devices to stages 345 and 346 which move vertically alongtracks (not shown) when motors 347 and 348, respectively, are energized.The angular orientation of devices 340 and 341 can be adjusted byloosening a thumbscrew and pivoting mounting plates 334 and 335,respectively. Plates 334 and 335 are mounted on manual positioningstages 343 and 344 that provide horizontal adjustment in the plane ofFIG. 33 when handles 336 and 337 are rotated. When the apparatus is inthe dispensing position adjacent tube 12′, the dispensing location ofthe needle tips can be adjusted by the aforementioned angular andhorizontal adjustment devices.

Stages 345 and 346 are mounted on a support member 350 which is mountedon a rotary stage 352 which rotates with respect to base 353 when motor354 is energized. Base 353 is affixed to stage 355 which is translatablealong track 356 in the x-direction when motor 357 is energized. Track356 is mounted to back plate 200 by mounting bracket 359.

Apparatus for positioning the UV light source is shown in FIG. 35. Lightis supplied to UV light sources 370 and 371 by light guide cables 372and 373, respectively. Sources 370 and 371 are affixed to a post 374that is connected to the top end of L-shaped support arm 377. Theopposite end of arm 377 is affixed to rotary stage 379 which rotatesupon base 380 when motor 378 is activated. Rotary stage base 380 ismounted to a linear stage 381 which moves vertically along track 382when motor 383 is activated. The resting position of arm 377 is shown inFIG. 35.

The operation of bottom clamps 69 can be understood by referring to FIG.5. Clamps 69, which are Sommer ultramatic cam-action grippers Model No.GP-19, are operated by a mechanism 390 which is mounted on an L-shaped.support arm 391. The support arm is affixed-to a linear stage 392 whichmoves vertically along track 393 when motor 394 is energized. Track 393is mounted on bottom draw stage 300.

Making a Coupler

Various 1×2 couplers including the 3 dB achromatic coupler disclosed inU.S. Pat. No. 5,011,251 (which is incorporated herein by reference) weremade by the process that is generally described below. The flametemperature, length of pull, and characteristics of the capillary tubeand optical fibers depend on the specific type of coupler being made. Tomake the coupler disclosed in U.S. Pat. No. 5,011,251 the two opticalfibers had different chlorine concentrations in their claddings. Theoutside diameters of the optical fiber and the protective coating were125 μm and 250 μm, respectively. Doped silica capillary tubes having alength of 34 mm, an inside diameter of 270 μm and an outside diameter of2.8 mm were utilized. Funnels at the ends of the tubes communicated withthe bore.

Referring to FIGS. 8, 9 and 10, a glass capillary tube 12 wastransferred from magazine 13 to V-groove members 86 where it was locatedagainst stop 89 by piston 88. Transfer clamps 92 were traversed in the−z direction until they surrounded tube 12. The clamps were actuated toengage tube 12, and stage 101 moved downwardly, whereby grooves 86withdrew from tube 12. Clamps 92 were then traversed in the +zdirection. Arm 107 rotated to position clamps 92 at coupler drawapparatus 63 where the tube was situated in front of draw chucks 64 and65. Transfer clamps 92 were traversed in the −z direction, and the endregions of the tube (now designated 12′) were placed in the V-grooves ofupper and lower chucks 64 and 65, respectively. The tube was secured byclamping bars 113 (FIGS. 11b and 12). The transfer clamps were thenretracted in the +z direction, and arm 107 was rotated to a verticalposition adjacent dispensing mechanism 82.

To deliver fiber 17 to guide tube 36, cyclinder 29 was actuated, therebyengaging roller 27 onto roller 24. Motor 25 turned roller 24 in theclockwise direction of arrow 24 a (FIG. 2). When a sufficient amount offiber had been delivered, idler roller 27 retracted from main roller 24,and cyclinder 31 was actuated to lower clamp 30 against bar 32 toprevent further movement of the fiber. During the time that fiber 17 wasbeing delivered, a position holding clamp (not shown) clamped fiber 16against bar 32 to prevent it's movement. During the delivery of fiber 17to guide tube 36, cylinder 31 was actuated to retract clamp 30 from bar32.

Motor 53 (FIG. 2) was energized to vertically position retaining tube 51such that guide tubes 35 and 36 and dispensing tube 44 were located justabove strip clamp 58. Motor 25 was rotated clockwise (arrow 24 a) andcylinders 29 and 31 were appropriately actuated to cause feed apparatus23 to deliver about 2-3 cm of coated fiber 17 from the end of guide tube36. Strip clamp 58 closed on the fiber. Motor 53 was energized to movethe guide tube upwardly to a position above strip clamp 57. The fiberwas pulled through guide tube 36 as the retaining tube 51 (and thusguide tube 36) moved upwardly. Strip clamp 57 closed on coated fiber 17.Cylinders 172 and 173 (FIG. 17) were actuated to tension the fiberbetween the strip clamps 57 and 58 for the coating strip operation.

Stripping nozzle 59 was rotated to a horizontal position and was loweredto a y position at which stripping was to start to occur. It was thenrotated about rotary mechanism 194 to position the end of nozzle 225(FIG. 20) adjacent the lower end of the region of coated fiber that wasto be stripped. The hot inert gas jet impinged on the coated fiber andthen moved upwardly and caused coating to be stripped from apredetermined region of the fiber (about 30 mm long) between the stripclamps. Stripping nozzle 59 rotated in the x-z plane to direct the hotjet-away from the coated fiber and then returned to its restingposition.

Ball termination torch 60 was lowered from its resting position positionto that level at which fiber 17 was to be severed; it then moved in the−z direction at 38.1 cm/minute. After it moved past the fiber, torch 60reversed direction and traversed the fiber at 3.81 cm/minute, wherebythe fiber became severed. Top clamp 57 moved upwardly about 1-2 mm, andbottom clamp 58 moved downwardly a few centimeters so that tapered end266 was out of the influence of the flame. As torch 60 continued to movein the. +z direction, a rounded, low reflectance termination was formedon tapered region 211a as described in conjunction with FIGS. 22-25.Strip clamps 57 and 58 were opened, and the small residual piece offiber was removed from clamp 58. After the end of fiber 17 had beenstripped and terminated, fiber 17 was retracted into guide tube 36.

Sometimes optical fiber has a characteristic referred to as “fiber curl”caused by unequal stresses on different sides of the fiber. This couldcause the end of fiber 17 which extends from clamp 57 to bend so that itis out of the influence of flame 260 after the fiber has been severed.This can be prevented by keeping the length of fiber extendingdownwardly from clamp 57 relatively short. To accomplish this, thedistance between clamps 57 and 58 should be relatively short, about 4 cmor less being suitable.

Retaining tube 51 was moved to a position such that guide tubes 35 and36 and dispensing tube 44 were located just above upper strip clamp 57.Stripping nozzle 59 was rotated to horizontal position, lowered androtated to a position where the hot jet was directed below dispensingtube 44. While the stripping nozzle remained stationary, fiber 16 wasfed from the guide tube 35 through the heated gas stream. After coatingmaterial was stripped from about 2.5-7.6 cm of the fiber, strippingnozzle 59 rotated away from the fiber, and all but about 1.3 cm of fiber16 was retracted into guide tube 35. Retaining tube 51 moved downwardlyuntil the end of fiber 16 enterd the capillary tube bore. Fiber 16 wasfed through tube 12′ until a length appropriate for forming a connectionpigtail (about 2 meters, for example) extended from the bottom of thetube. Drops of ethyl alcohol were delivered from dispensing tube 44while fiber was being fed through tube 12′. The end of fiber 16 that hadbeen end stripped was cleaved, and the cleaved end was put into a camoperated fiber splice assembly tool to temporarily connect it to lightsource fiber 47 of measurement system 46.

Retaining tube 51 was retracted from tube 12′, and fiber 16 wasdelivered at the same speed so there was no relative movement betweenfiber and tube. When guide tube 35 was above strip clamp 57, strip clamp58 closed; strip clamp 57 then closed. The air cylinders 172 and 173were actuated to tension the fiber between the strip clamp 57 and 58 forthe coating strip operation.

A section of coating was stripped from fiber 16 in the same manner aspreviously discussed in connection with fiber 17. The resultant bareregion was slightly shorter than the length of tube 12′ (about 30 mm).Strip clamps 57 and 58 then released the fiber.

Through fiber 16 was retracted until the stripped region remained about0.6 cm from the end of the guide tube 35. The retaining tube and guidetubes were not moving downward toward tube 12′ at this time.

Bottom clamp 69 closed on that portion of fiber 16 extending from thebottom of tube 12′. Motors 53 and 394 were energized, and retaining tube51 and bottom clamp 69 moved downwardly at the same rate. Drops ofalcohol were fed from dispensing tube 44 as the stripped regions offibers 15 and 16 were simultaneously lowered toward tube 12′. Asretaining tube 51 was moved toward tube 12′, the stripped end of fiber17 was fed from guide tube 36 until the end of fiber 17 was positionedat about the center of the stripped region of fiber 16. At this timefiber 17 was no longer fed from guide tube 36, and both fibers wereadvanced downwardly by movement of retaining tube 51 and lower clamp 69until the stripped midregion of fiber 16 was centered in the bore oftube 12′. At this time the tip of fiber 17 was located at about thelongitudinal center of tube 12′. Fiber 17 was then fed from guide tube36 until the bare region thereof extended adjacent the strippedmidregion of fiber 16 through tube midregion 399 as shown in FIG. 36.

If the bare region of fiber 17 were positioned adjacent the bare regionof fiber 16 above tube 12′, and both fibers advanced together into thebore of tube 12′, the surface tension of the alcohol could cause thebare region of fiber 17 to twist about the bare region of fiber 16. Thiscould affect process reproducibility. The solution to the problem is todeliver the fibers as described above such that the bare region of fiber16 is positioned in the tube bore first, the tip of fiber 17 beingmidway down the tube bore and thereafter advancing the bare portion offiber 17 the remainder of the distance into the bore until both fibersare positioned as shown in FIG. 36.

Bottom vacuum seal 67 was closed, and alcohol was evacuated from thebore of tube 12′. During this step, which lasted about 20-60 seconds (20seconds being typical), air was pulled through the bore of tube 12′. Airwas also bled into left vacuum seal 67 through valve 77.

During the vacuum purge of alcohol from the tube bore, a referencemeasurement was made by system 46.

Retaining tube 51 was raised and fibers 16 and 17 were fed through tubes35 and 36 at the same rate until the bottoms of tubes 35, 36 and 44cleared the top vacuum seals 66.

The top vacuum seals closed, and the bore of tube 12′ was evacuated. Airwas bled through valve 76 and into one side of the vacuum seal 66 whilethe other side of vacuum seal 66 was evacauated. This generated a fastmoving air stream that removed any alcohol that had accumulated on thetop of tube 12′.

The aspirator function, i.e. the bleading of air through valves 76 and77, occurs at any time that vacuum seals are closed. The aspiratorfunction occurs not only during alcohol removal but also during theevacuation of the tube bore during the later described steps ofcollapsing the tube onto the fibers and stretching the tube to form acoupler. This is not detrimental to the tube collapse step since only alow level of vacuum is required during that step.

With methane flowing at a rate of 0.5 slpm (full operating level) andoxygen flowing at a rate of 0.1 slpm (a level below operating level),burner sections 310 and 311 were ignited. Cylinder 327 was actuated tomove split burner 68 in the −x direction, whereby burner sections 310and 311 were positioned such that tube 12′ was centered within annularregions 316 and 317 (FIGS. 30-32). Burner close mechanism 314 was thenactuated to cause sections 310 and 311 to close around tube 12′. At thattime the flow of oxygen was increased to full operating level (1 slpm),and the midregion 399 (FIG. 36) of tube 12′ was heated to a sufficientlyhigh temperature to cause it to collapse onto the fibers. The vacuum atthis time was 27.9 cm of mercury. About 15-30 seconds after theapplication of the full intensity flame to, tube 12′ (typically 22seconds for the first pull), stage 299 moved upwardly and stage 300moved downwardly, whereby the top and bottom chucks 64 and 65 weretraversed in opposite directions a total of 13 mm. As soon as the stagesstarted to pull the coupler, the programmable controller reduced theflow of oxygen to the burner to zero in 1 second. Since retaining tube51 and bottom clamps 69 are mounted on upper and lower draw stages 299and 300, respectively, they also move the same distance as chucks 65 and66, respectively.

Burner 68 opened and retracted in the +x direction away from tube 12′.

The first pull was intentionally performed such that less than thedesired coupling was obtained. An optical measurement was made todetermine the amount of coupling that resulted from the first pull. Thisinformation was input to the programmable controller, and a second pullwas performed.

The burner flame was ignited as described above, and the burner againmoved in the −x direction and closed about the tube. About 2-10 secondsafter the application of the full intensity flame to the tube (typicallyabout 8 seconds), the top and bottom chucks 64 and 65 were againtraversed in opposite directions a total of 2.6 mm. As soon as thestages started to pull the coupler, the programmable controller reducedthe flow of oxygen to the burner to zero in 0.75 second. The burneropened and retracted in the +x direction. The burner was shut off.

The combination of the-tube collapse and stretch steps resulted in theformation of a coupler 400 (FIG. 37) having a tapered coupling region401. The length of the coupler was 49.6 mm.

The vacuum seals were opened.

The epoxy was stored in reservoirs 360 and 361 which were attached tosupport member 350. Pressure controllers 362 and 363 pressurizedreservoirs 360 and 361 at 24 psi and 33 psi, respectively. The epoxy wasa mixture of the following components: (a) 33.11 weight percent ELC2500, an epoxy resin/photoinitiater blend made by Electrolite Corp.,Danbury, Conn., (b) 0.34 weight percent additional photoinitiator, (c)58.23 weight percent magnesium pyrophosphate filler (screened to 35 μm),and (d) 8.32 weight percent 1.5 μm silica microspheres made by GeltechCorp., Alachus, Fla. The viscosity of the epoxy at 25_(E)C, 58_(E)C and82_(E)C is approximately 80 poise, 10-15 poise and 4 poise,respectively.

Rotary stage 352 rotated 90_(E) (in the counter-clockwise direction whenobserved from the top or +y direction) to position devices 340 and 341farther away from apparatus backplate 200 so that the epoxy applicationapparatus would clear other equipment as it traverses toward the drawapparatus 63. Stage 355 then moved in the −x-direction, and rotary stage352 rotated further in the above-described direction. This positionedepoxy application devices adjacent coupler 400 (FIG. 37) with thedispensing needles 338 and 339 vertically removed from the ends of thecoupler. Motors 347 and 348 were energized to position the needlesadjacent the funnels as illustrated in FIG. 37. The needles can bepositioned at (immediately above or into) the funnel during epoxydispensing.

The angular orientation of top needle 338 did not seem to be critical.The size of needle 338 was 22 gauge. With the end of the needlepositioned immediately above the top funnel, actuator 340 was energized1.75 seconds to deliver a drop of epoxy which, assisted by gravity andcapillary action, flowed into the top funnel and into the top bore.

When a needle 339 of similar size was employed to apply epoxy to thebottom funnel, an insufficient amount of epoxy traveled into the bore.Reasons for this are as follows. The ends of the tube reach a maximumtemperature of about 95_(E)C during the last stretch step. At the timethat the epoxy is applied, the temperature of the top and bottom of thetube has decreased to about 82_(E)C and 58_(E)C, respectively. Moreover,the temperature continues to decrease as the epoxy is being applied.This causes the viscosity of the epoxy in the bottom funnel to be higherthan that in the top funnel as mentioned above. Also, the epoxy in thebottom funnel must flow upwardly. The following steps were taken toensure the proper application of epoxy to the bottom funnel and bore.The epoxy applied to the bottom funnel was supplied at a higherpressure, and bottom needle 339 was smaller than needle 338, needle 339being a size 18 gauge. Needle 339 was oriented at an angle of about30_(E) from vertical. In general, needle 339 should be oriented lessthan 45_(E) from vertical. This enables the tip of needle 339 to bepositioned deep in the funnel as shown in FIG. 37. In addition, the tipof needle 339 is beveled such that its opening is oriented horizontallyor nearly horizontally. This causes the epoxy to be directed up thefunnel toward the bore. Since the epoxy is applied to the bottom funnelat higher pressure through a smaller needle, it squirts up into thefunnel and reaches the bore where it flows upwardly under the influenceof capillary action as well as the force caused by a pressure reductionin the bore due to the cooling of the coupler. The same amount of epoxyis applied to the top and bottom funnels. Because of the small needlesize, the flow rate into the bottom funnel was lower; therefore, theactuator 341 was energized 4.2 seconds to deliver a similar drop ofepoxy to the bottom funnel.

After a drop of epoxy was injected into each funnel, the needles wereretracted vertically from the funnels and were moved away from thelongitudinal axis of tube 12′. This caused the epoxy drops to releasefrom the needles. The first application of epoxy was insufficient tocompletely fill the funnels. If the funnels had been completely filled,an air bubble could have formed and prevented the epoxy from advancing asufficient distance into the bores. UV light from sources 297 caused theepoxy to cure and cease flowing after it had flowed a predetermineddistance into the bores.

After about 3-10 seconds (5 seconds is typical) had elapsed to permitthe epoxy to traverse through the funnels and into the tube bores bycapillary action, needles 338 and 339 were again positioned at thefunnels. A second drop of epoxy was dispensed into each funnel; thisdrop was sufficient to fill each funnel. The epoxy application apparatusthen moved to resting position. The epoxy filled the funnels, which wereabout 2.5 mm deep and extended into the bores a distance of about 3.5mm.

In the resting position of arm 377 (FIG. 35) UV light sources 370, 371are at the same vertical level as upper chuck 64. Motor 378 is activatedto rotate arm 377 in the direction of arrow 385. When in its fullyrotated position, sources 370 and 371 are located immediately above andbelow upper clamping bar 113. After the temperature of the coupler isbelow 40_(E)C, UV light sources 370,371 are energized to cure the epoxyin the upper end of tube 12′. The upper clamping bar 113 is optionallyopen during the time that sources 370, 371 are positioned at the upperend of tube 12′. The period between the time that the coupler has beenheated for stretching purposes and the time that the temperature of thecoupler has dropped below 40_(E)C can be determined empirically. Arm 377is rotated to retract light sources 370 and 371 a sufficient distance toclear the equipment. Motor 383 is energized to lower the light sourcesto a level such that when arm 377 is again rotated in the direction ofarrow 385 those sources will be immediately above and below lowerclamping bar 113 to cure the epoxy in the lower end of coupler 400. MoreUV light will reach the epoxy if the lower clamping bar 113 is open atthis time.

When the coupler is sufficiently cool (30-45 sec) an optical measurementis made.

The coupler body is released from the draw chucks.

The fiber pigtails at the top of the coupler are metered out by thefiber feed apparatus until about 2 m of fiber extends from the top endof the coupler. The output pigtails are then severed by a cutting toolor by bending fibers 16 and 17 to a tight radius at the ends of guidetubes 35 and 36. Coupler 400 is removed from the draw.

The specific example concerns the formation of 1×2 couplers. Theabove-described manufacturing apparatus could also be employed to make1×N couplers of different configurations such as the 1×6 and 1×8, forexample. To make a 1×6, guide tubes 410 could be arranged in asix-around-one configuration within a retaining tube 411 (FIG. 38). Morethan one alcohol dispensing tube could be employed. Also, since it maybe desirable to maintain the guide tubes in the illustrated close packedarray, the alcohol dispensing tubes can be situated outside theretaining tube. Three dispensing tubes 412 are shown as being equallyspaced around the retaining tube.

To make a 1×8, guide tubes 420 could be arranged in an eight-around-oneconfiguration within a retaining tube 421, a spacer tube surrounding thecentral guide tube (FIG. 39). Three dispensing tubes 422 are equallyspaced around retaining tube 421.

A semi-automatic coupler manufacturing apparatus could employ some ofthe components shown in FIGS. 4 and 5. The most important components arethe fiber feed and insertion devices. When the disclosed fiber feeddevice is employed, the disclosed vacuum chucks are extremely useful,since the fibers extending from tube 12′ are connected to the measuringsystem and are extending through the feed tubes. However, the tube 12′could be manually inserted into the chucks. If this were done, thechucks could be of different design. Further, a ring burner could beemployed if manual tube insertion were employed. A tube would beinserted through the ring burner and then chucked at its ends. After thecoupler is formed, it could be released from the chucks, and the epoxycould be applied and cured off-line.

The duplication of certain functions would decrease the time required tomake a coupler. FIG. 40 shows how apparatus 10 could be modified byemploying two stripping and terminating stations 430 and 431. Each ofthe stations 430 and 431 is provided with a stripping nozzle, a balltermination torch and a pair of clamps similar to clamps 57 and 58.Tracks 54 and 54 a are affixed to a stage 432 that moves horizontallyalong track 433. In the situation represented by FIG. 40 fiber insertionapparatus 50 had previously been located adjacent stripping andtermination station station 430 so that the fibers within the fiberguide tubes of apparatus 50 have been prepared for insertion into tube12′. Stage 432 has therefore moved to the position shown so that thefibers can be inserted into the tube. Thus, fiber insertion apparatus 50a is located adjacent stripping and termination station station 431 sothat the fibers within the fiber guide tubes of apparatus 50 a can beprepared for insertion into tube 12′. After the coupler is formed byemploying fibers from apparatus 50, stage 432 moves to the left, anothertube 12′ is inserted into chucks 64, and the fibers from apparatus 50 aare inserted into the tube.

The fiber feed apparatus and fiber insertion apparatus shown in FIGS. 2,15 a, 15 b and 16 allows one or more fibers to be manipulated remotelywhile at the same time controlling their absolute position andorientation with respect to a given location and eachother. Such anapparatus could also be employed to position an optical fiber at morethan one work station, each of which performs one or more procedures onthe fiber. FIG. 41 shows a guide tube 440 in which coated optical fiber441 is situated. The guide tube can be part of the apparatus shown inFIG. 40 whereby it can be moved vertically or horizontally as indicatedby arrows 444 and 443, respectively. In addition, fiber 441 can traversethrough tube 440 in either direction as indicated by arrow 442.

The first work station 445 could be one containing a. stripping nozzlefor stripping coating material from the end of fiber 441. The fibercould be retracted into tube 440, and that tube could be moved to secondwork station 446 where the stripped end could be inserted into agrinding machine that forms a lens on the end of the fiber. The lensedfiber could be retracted into tube 440 and moved to third work station447 where a layer of gold could be deposited thereon by sputtering orthe like. The resultant fiber would be suitable for use as a laser diodepigtail. The gold layer enables the fiber to be soldered to a fixturewith the lensed end in light receiving relationship with the laserdiode.

We claim:
 1. An apparatus for applying glue to a fiber optic coupler of the type composed of a plurality of contiguously extending optical fibers, said fibers extending through the bore of a tube and through a longitudinally adjacent coupling region where the tube is collapsed around the fibers, said fibers being fused together in said coupling region, the diameters of said fibers in said coupling region being smaller than the diameters thereof in said bore, said apparatus comprising: means for holding said coupler, and means for simultaneously injecting glue into both ends of said tube bore; wherein said means for injecting comprises: first and second hollow needles, means for positioning one of said needles at each end of said tube bore, and first and second sources of glue respectively connected to said first and second needles; wherein said tube is held vertically so that it has upper and lower ends, the inner diameter of said first needle that is insertable into said bottom end being smaller than that of said second needle that is insertable into said top end.
 2. The apparatus of claim 1 wherein the tip of said first needle is bevelled such that said first needle is disposed at an angle with respect to the longitudinal axis of said tube. when said first needle is positioned in said bore, and the bevelled end of said first needle lies in a plane that substantially perpendicular to said longitudinal axis.
 3. The apparatus of claim 2 wherein said first needle is disposed at an angle less than 45_(E) with respect to said longitudinal axis when said first needle is positioned in said bore.
 4. A method for applying glue to a fiber optic coupler composed of a plurality of contiguously extending optical fibers, said fibers extending through the bore of a tube and through a longitudinally adjacent coupling region where the tube is collapsed around the fibers, said fibers being fused together in said coupling region, the diameters of said fibers in said coupling region being smaller than the diameters thereof in said bore, said method comprising: holding said coupler, and simultaneously injecting glue into both ends of said tube bore; wherein said coupler is oriented vertically, said glue being injected into said bore ends by positioning a hollow needle at each of said bore ends, said glue flowing through the needle in the bore at the top end of said tube at a rate greater than it flows through the needle in the bore at the bottom end of said tube.
 5. The method of claim 4 wherein said glue is injected into said bore ends by positioning a hollow needle at each of said bore ends, flowing glue through said needles and retracting said needles so that a first drop of glue is inserted into each end of said bore, again positioning said needles at each end of said bore, flowing glue through said needles and retracting said needles so that a second drop of glue is inserted into each end of said bore.
 6. The method of claim 5 wherein, during the injection of glue into the ends of said bore, an ultraviolet light beam is directed to each end region of said tube. 